I'm assuming you're using
if (isset($_POST['submit'])) {
If so, then for your HTML-only form just give the submit button a different name, like
<input type="submit" name="reiterate">
Then you would have separate blocks of code depending on which submit button was pressed.
if (isset($_POST['submit'])) {
...
//submit and insert data into database
...
}
elseif (isset($_POST['reiterate'])) {
...
//display form with values from other form
...
}
else {
//Show blank form
}